Capacitance detection device and driving method of the same

ABSTRACT

Disclosed a driving method for a capacitance-detection device, the method including: acquiring a noise signal; comparing a magnitude of an acquired noise signal with a threshold value for driving a capacitance-detection device; and adjusting a driving signal, provided to a capacitance-detection device to be driven, according to a result of said comparing. The acquiring the noise signal includes: generating the noise signal corresponding to detected noise; and converting the noise signal into a digital signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/872,503, filed on Jan. 16, 2018, which claims priority from and thebenefit of Korean Patent Application No. 10-2017-0020076, filed on Feb.14, 2017, the disclosure of which are incorporated herein by referencein their entirety.

BACKGROUND 1. Field of the Invention

The present invention relates to a capacitance-detection device and adriving method of the same.

2. Discussion of Related Art

Sensing methods configured to detect touch are mainly based on resistivesensing, surface ultrasonic sensing, and capacitive sensing. Capacitivesensing methodology enables multi-touch sensing and has excellentdurability, visibility, and the like. Therefore, capacitive sensing isbeing increasingly adopted as a main input means for portable mobiledevices.

A capacitive capacitance-detection device senses, in operation, a changein amount of charge electrified in capacitive sensors on a touch screenpanel, as caused by a user interference, to recognize a user input.According to charge accumulation methods, capacitivecapacitance-detection devices are classified into a self-capacitive typeand a mutual-capacitive type. In the self-capacitivecapacitance-detection device, one capacitive sensor constitutes oneconductor to form a reference ground and an electrified surface outsidea touch screen panel, whereas, in the mutual-capacitivecapacitance-detection device, two conductors on a touch screen panelconstitute function as capacitive sensor.

In a general self-capacitive capacitance-detection device, an orthogonalX/Y conductor disposition is used. In this case, each capacitive sensorfunctions as a line sensor, and thus upon each touch screen sensing,such capacitive sensor receives only one portion of X-sensinginformation and one portion of Y-sensing information from an X-linesensor group and a Y-line sensor group, respectively. Therefore, ageneral self-capacitive touch screen is configured to be capable ofsensing and tracking a single touch but cannot support performanceinvolving multiple touches.

In a mutual-capacitive capacitance-detection device, the orthogonal X/Yconductor disposition is used as well. However, the mutual-capacitivecapacitance-detection device differs from the self-capacitivecapacitance-detection device in that each capacitive sensor in theformer is configured as a grid sensor at each position where conductorscross each other at right angles, and reactions of all grid sensors areseparately sensed upon detection of a user input on a touch screen.Since grid sensors correspond to different pairs of X/Y coordinates on aone-to-one basis and provide independent reactions to inputs, amutual-capacitive touch screen may be used to sense and track multipletouches of a user by extracting user input information from a set ofX/Y-sensing information received from a set of X/Y grid sensors.

A conductor configuration of and a sensing method carried out by ageneral mutual-capacitive touch screen panel are as follows. Firstelectrodes (composed of conductors extending in one direction) andsecond electrodes (composed of conductors extending in a directionperpendicular to that of the first electrodes) form mutual-capacitivesensors, with the use of a dielectric material between the first andsecond electrodes as a medium. When the distance between first andsecond electrodes of each pair is d, the area of each surface is a, andthe equivalent permittivity of all dielectric materials betweenelectrified surfaces is ε, a capacitance C of each of the sensors isdefined as C=ε*a/d and has a relationship with an amount Q of chargeaccumulated in the sensor and a potential difference (voltage) V appliedto the two electrodes/electrified surfaces, via Q=CV. When a userapproaches such a sensor, interference occurs in an electric fieldformed between the two electrodes and hinders charge from beingaccumulated in the sensor. Then, the amount of charge accumulated in thesensor is reduced, and as a result, the capacitance of the sensor isreduced. This may be understood and/or viewed as a change of thecapacitance resulting from a change in the equivalent permittivitybetween electrified surfaces caused by the approach of the user, butthere is actually a physical phenomenon that a part of an electric fieldbetween the electrified surfaces is shunted and thus the amount ofelectrification/accumulated charge is reduced. When an alternatingcurrent (AC) voltage source is connected to the first electrode and anAC waveform is applied to one electrified surface of the sensor, achange ΔQ in the amount of electrification corresponding to ΔQ=CΔVoccurs with respect to C that varies according to the degree of approachof the user, and that is converted into a current or voltage by aread-out circuit connected to the second electrode. Informationconverted in this way is generally subjected to signal processingoperations (such as noise filtering, demodulation, analog-to-digitalconversion, accumulation, and the like), and then is used in acoordinate-tracking algorithm and a gesture-recognition algorithm. As apreceding patent relating to such a capacitive touch-sensitive panel,there is U.S. Pat. No. 7,920,129.

SUMMARY

Capacitance-detection devices are used in various fields, such as aportable phone, a tablet, a portable personal computer (PC), and thelike. As a user, who carries a capacitance-detection device, moves, thecapacitance-detection device operates in various environments.Therefore, the capacitance-detection device is affected by noise comingfrom an environment thereof, and accordingly detection of an inputprovided by the user is affected.

The present embodiments are directed to providing acapacitance-detection device and a driving method of the same, whichmake it possible to reduce influence of noise whereby detection of auser's input is affected.

According to an embodiment of the present invention, there is provided adriving method for a capacitance-detection device, the method including:acquiring a noise signal; comparing a magnitude of such acquired noisesignal and a threshold value for driving a capacitance-detection device;and adjusting a driving signal provided to a capacitance-detectiondevice to be driven according to a result of such comparison.

Another embodiment of the present invention provides acapacitance-detection device including: a capacitance-detection panelcontaining driving electrodes and sensing electrodes; a driving circuitconfigured to provide a driving signal to the driving electrodes and toreceive a capacitance-detection signal from the sensing electrodes; anda noise-detection probe configured to detect and provide noise to thedriving circuit. The driving circuit adjusts the driving signalaccording to a magnitude of the detected noise.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent to those of ordinary skill in theart by describing in detail embodiments thereof with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic diagram showing a summary of acapacitance-detection device according to the present embodiment;

FIG. 2 is a flowchart illustrating a summary of a capacitance-detectionmethod according to the present embodiment;

(a) of FIG. 3 is a diagram showing a summary of a configuration of acapacitance-detection panel according to an embodiment;

(b) of FIG. 3 is a diagram schematically showing provision of a drivingsignal to a driving electrode according to the embodiment;

(c) of FIG. 3 is a diagram showing a summary of a configuration of acapacitance-detection panel according to another embodiment;

(d) of FIG. 3 is a diagram schematically showing provision of a drivingsignal to a driving electrode according to the other embodiment;

FIG. 4 is a block diagram showing a summary of a driving circuit;

FIG. 5 is a schematic diagram showing an example of a noise-detectionprobe;

FIG. 6 is a diagram exemplifying changes in the magnitude of a noisesignal detected by a noise probe over time in relation to a plurality ofthreshold values;

FIG. 7 is a timing diagram exemplifying period-specific changes of adriving signal provided to a capacitance-detection panel; and

FIG. 8 is a diagram showing noise levels detected by acapacitance-detection device and a driving method of thecapacitance-detection device according to the present embodiment

DETAILED DESCRIPTION

Hereinafter, a capacitance-detection device and a driving method for thesame according to the present embodiment will be described in detailwith reference to the accompanying drawings. FIG. 1 is a schematicdiagram summarizing a capacitance-detection device 10 according to thepresent embodiment. Referring to FIG. 1, the capacitance-detectiondevice 10 includes a capacitance-detection panel 100 including drivingelectrodes Tx1, Tx2, . . . , and Txn and sensing electrodes Rx1, Rx2, .. . , and Rxn (see FIG. 3), a driving circuit 200 that provides adriving signal to the driving electrodes and receives acapacitance-detection signal from the sensing electrodes, and anoise-detection probe 300 which detects and provides noise to thedriving circuit. The driving circuit 200 adjusts the driving signalaccording to a magnitude of the detected noise.

In the embodiment shown as an example in FIG. 1, the noise-detectionprobe 300 is configured to detect noise Vnoise_(LCD) (coming from aliquid crystal display (LCD) to the capacitance-detection device 10),noise Vnoise_(ENV) (coming from an environment in which thecapacitance-detection device 10 is located), and low-frequency noiseVnoise_(Low Freq.) (coming from a power source and the like), and toprovide a signal corresponding to the detected noise to the drivingcircuit 200.

FIG. 2 is a flowchart illustrating a capacitance-detection methodaccording to the present embodiment. Referring to FIG. 2, a drivingmethod for a capacitance-detection device according to the presentembodiment includes: acquiring a noise signal (S100), comparing amagnitude of the acquired noise signal and a threshold value for drivinga capacitance-detection device (S200), and adjusting a driving signalprovided to a capacitance-detection device to be driven according to aresult of such comparison (S300).

(a) of FIG. 3 is a diagram summarizing a configuration of thecapacitance-detection panel 100 according to an embodiment, and (b) ofFIG. 3 is a diagram schematically showing how a driving signal isprovided to a driving electrode according to such embodiment. (c) ofFIG. 3 is a diagram summarizing a configuration of thecapacitance-detection panel 100 according to another related embodiment,and (d) of FIG. 3 is a diagram schematically showing how a drivingsignal is provided to a driving electrode according to such relatedembodiment. Referring to (a) of FIG. 3, the capacitance-detection panel100 includes a substrate Sub, a plurality of driving electrodes Tx1,Tx2, . . . , and Txn disposed on one side of the substrate Sub, and aplurality of sensing electrodes Rx1, Rx2, . . . , and Rxn disposed onthe other side of the substrate Sub.

In (a) of FIG. 3, the capacitance-detection panel 100 may furtherinclude a noise-detection probe 300. In the embodiment, thenoise-detection probe 300 may be any one of a driving electrode and asensing electrode formed in the capacitance-detection panel 100. Thenoise-detection probe 300, in operation, detects noise and generates andprovides a noise signal (corresponding to the detected noise) to thedriving circuit 200.

Referring to (b) of FIG. 3, the driving electrodes Tx1, Tx2, . . . , andTxn formed on the one side of the substrate Sub form capacitors with thesensing electrodes Rx1, Rx2, . . . , and Rxn at intersections, and thecapacitors are referred to as mutual capacitances Cm. In other words,the driving electrodes are one electrodes of the capacitors, and thesensing electrodes are the other electrodes thereof. A driving signal isprovided to a driving electrode such that electric fields E are formedbetween the driving electrode and the sensing electrodes. The space, inwhich the electric fields are formed, corresponds to a dielectricmaterial of the capacitances. (b) of FIG. 3 schematically shows that adriving signal is provided to Tx2 such that electric fields are formedbetween Tx2 and the crossing sensing electrodes Rx1, Rx2, . . . , andRxn and mutual capacitors CM are formed.

(c) of FIG. 3 schematically shows an embodiment of a panel, in whichdriving electrodes Tx1, Tx2, . . . , and Txn and sensing electrodes Rx1,Rx2, . . . , and Rxn are disposed on the same side of the substrate Sub.Each driving electrode includes diamond patterns and connection lineswhich connect the diamond patterns, and each sensing electrode includesdiamond patterns and connection lines which connect the diamondpatterns. The diamond patterns of the driving electrodes and the diamondpatterns of the sensing electrodes do not come into contact with eachother, and an insulating material is interposed between the connectionlines of the driving electrodes and the connection lines of the sensingelectrodes so that the connection lines of the driving electrodes andthe connection lines of the sensing electrodes are not short-circuited.

In the embodiment shown in (c) of FIG. 3, the capacitance-detectionpanel 100 may further include a noise-detection probe 300. In theembodiment, the noise-detection probe 300 may be any one of a drivingelectrode and a sensing electrode formed in the capacitance-detectionpanel 100. The noise-detection probe 300 detects noise and generates andprovides a noise signal corresponding to the detected noise to thedriving circuit 200.

Referring to (d) of FIG. 3 which is a cross-sectional view of the panelof (c) of FIG. 3 taken along line B-B′, when a driving signal is appliedto a driving electrode Txn, each diamond of the driving electrode formsan electric field with an adjacent sensing electrode, and accordinglyforms a mutual capacitance CM. (d) of FIG. 3 shows that Txn forms mutualcapacitances with sensing electrodes Rx1 and Rx2.

FIG. 4 is a block diagram showing a summary of the driving circuit 200.Referring to FIG. 4, the driving circuit 200 includes a driving signalprovider 210 including a signal source Vsig which provides a drivingsignal to the capacitance-detection panel 100, and a driving controller220 which receives a noise signal collected by the noise-detection probe300, compares the noise signal and a threshold value for driving acapacitance-detection device, and determines a driving signal V_(TX) anda driving electrode to which the driving signal V_(TX) is provided.

In an embodiment, the driving signal provider 210 includes the signalsource Vsig which generates the driving signal V_(TX), and a multiplexer(MUX) 212 which multiplexes the provided driving signal and provides themultiplexed driving signal to a driving electrode of thecapacitance-detection panel 100 (see FIG. 1).

In an embodiment, the driving controller 220 includes a charge amplifier222, which is operation receives and amplifies a noise signal providedby the noise-detection probe 300, an analog-to-digital converter (ADC)224 configured to convert a signal provided by the charge amplifier 222into a digital signal, and a controller 226 that is operation receivesthe digitized noise signal, compares the digitized noise signal with thethreshold value for driving a capacitance-detection device, and controlsa driving signal provided to the capacitance-detection panel 100.

FIG. 5 is a schematic diagram showing an example of the noise-detectionprobe 300. Referring to FIG. 5, the capacitance-detection device 10according to the present embodiment may be implemented in the form of anintegrated circuit (IC) 10′, and the noise-detection probe 300 may be apin of the IC 10′.

As an example, the pin which functions as the noise-detection probe 300is in an electrically floating state and functions as an antenna whichcollects noise. As another example, a reference voltage which isprovided to the IC 10′ is provided to the pin functioning as thenoise-detection probe 300 such that inflowing noise may be detectedthrough the reference voltage. As another example, the noise-detectionprobe 300 may be any one of a driving electrode and a sensing electrodeof a capacitance-detection panel (see FIG. 3) as described above.

A driving method for a capacitance-detection device and operation of thecapacitance-detection device according to the present embodiment will bedescribed below with reference to FIGS. 6 and 7. FIG. 6 is a diagramexemplifying changes in the magnitude of a noise signal N detected bythe noise-detection probe 300 over time in relation to a plurality ofthreshold values, and FIG. 7 is a timing diagram exemplifyingperiod-specific changes of a driving signal provided to thecapacitance-detection panel 100. In FIGS. 6 and 7, it is assumed that acapacitance-detection panel including eight driving electrodes isdriven, and those of ordinary skill in the art may easily modify thepresent embodiment into a driving method of a capacitance-detectionpanel including a more or less number of driving electrodes.

Referring to FIGS. 6 and 7, the controller 226 receives the digitizednoise signal N from the ADC 224 and compares the noise signal N with aplurality of threshold values. During period {circle around (1)}, amagnitude of the noise signal N is less than a first threshold valueTh.1. When the noise signal N has a magnitude less than the firstthreshold value Th.1, it is possible to obtain a signal-to-noise ratio(SNR) required to distinguish a user input even if driving electrodesare sequentially driven. Therefore, the driving electrodes aresequentially driven.

However, when the magnitude of the noise signal N increases and exceedsthe first threshold value Th.1 but is less than a second threshold valueTh.2 as shown in period {circle around (2)}, it is not possible toobtain a sufficient SNR to distinguish a user input if the drivingelectrodes are sequentially driven like in period {circle around (1)}.

The controller 226 increases a sensing time t_(sense2) in period {circlearound (2)} to be longer than a sensing time t_(sense1) in period{circle around (1)}. A touch signal generated by a touch is accumulatedwith an increase in sensing time such that a magnitude of the touchsignal increases. However, since noise theoretically has an averageamplitude value of 0, a magnitude of the noise signal does not increasewith an increase in sensing time. Therefore, it is possible to obtain asufficient SNR to distinguish a user input by increasing a sensing time.However, the controller 226 uniformly maintains an operating rate of thecapacitance-detection panel by uniformly maintaining a time in which allthe driving electrodes are driven. As an implementation example, thecontroller 226 may increase the sensing time t_(sense2) in period{circle around (2)} to double the sensing time t_(sense1) in period{circle around (1)} and simultaneously provide a driving signal to thefirst driving electrode Tx1 and the second driving electrode Tx2.

When the magnitude of the noise signal N further increases and exceedsthe second threshold value Th.2, it is not possible to obtain asufficient SNR by detecting a user input during the sensing timet_(sense2) in period {circle around (2)}. Therefore, the controller 226may increase a sensing time t_(sense3) in period {circle around (3)} tobe longer than the sensing time t_(sense) 2 in period {circle around(2)}. Also, the controller 226 uniformly maintains the operating rate ofthe capacitance-detection panel by uniformly maintaining the time inwhich all the driving electrodes are driven.

As an implementation example, the controller 226 may increase thesensing time t_(sense3) in period {circle around (3)} to double thesensing time t_(sense2) in period {circle around (2)} and simultaneouslydrive the first driving electrode Tx1, the second driving electrode Tx2,the third driving electrode Tx3, and the fourth driving electrode Tx4.Subsequently, the controller 226 may simultaneously drive the fifthdriving electrode Tx5, the sixth driving electrode Tx6, the seventhdriving electrode Tx7, and the eighth driving electrode Tx8.

In the embodiment shown in FIGS. 6 and 7, two different threshold valuesare used to sequentially drive the driving electrodes, or the drivingelectrodes are classified into groups of two driving electrodes orgroups of fourth driving electrodes, and the groups are sequentiallydriven.

However, according to an embodiment not shown in the drawings, a morenumber of threshold values are used to sequentially drive the drivingelectrodes, or the driving electrodes are classified into groupsincluding two driving electrodes, groups including three drivingelectrodes, . . . , or a group including seven driving electrodes, andthe groups are sequentially driven.

Simulation Example

FIG. 8 is a diagram showing noise levels detected by acapacitance-detection device and a driving method of thecapacitance-detection device according to the present embodiment.Referring to FIG. 8, an upper solid line indicates a noise leveldetected by providing a driving signal to one driving electrode, amiddle solid line indicates a noise level detected by sequentiallyproviding a driving signal to four driving electrodes, and a lower solidline indicates a noise level detected by sequentially providing adriving signal to 16 driving electrodes.

When sensing is performed while four single driving electrodes aredriven by simultaneously providing a driving signal to the four drivingelectrodes, it is possible to see that a noise signal is averaged outand the noise level is lowered. Also, when sensing is performed while 16single driving electrodes are driven by simultaneously providing adriving signal to the 16 driving electrodes, it is possible to see thata noise signal is averaged out and the noise level is further lowered.

Consequently, according to the present embodiment, since it is possibleto detect a user input by dynamically changing a sensing time accordingto a magnitude of a noise signal acquired by a noise-detection probe, areduction in SNR can be prevented in spite of the inflow of noise.

According to the present embodiment, it is possible to reduce aninfluence of noise coming into a capacitance-detection device ondetection of a user input such that the user input can be detected withhigh sensitivity and accuracy.

Although embodiments of the present invention have been described indetail above with reference to the accompanying drawings, the presentinvention is not limited to these embodiments and may be practiced in avariety of modified ways without departing from the technical spirit ofthe present invention. Therefore, the embodiments disclosed in thepresent invention are intended not to limit but to describe thetechnical scope of the present invention, and the scope of the technicalspirit of the present invention is not limited by the embodiments. Theembodiments set forth herein should be construed as not limiting. Thescope of the present invention is disclosed in the following claims, andall technical spirits within the range of their equivalents shall beconstrued as being included in the scope of the present invention.

What is claimed is:
 1. A driving method for a capacitance-detectiondevice, the method comprising: (a) acquiring a noise signal; (b)comparing a magnitude of an acquired noise signal with a threshold valuefor driving a capacitance-detection device; and (c) adjusting a drivingsignal, provided to a capacitance-detection device to be driven,according to a result of said comparing.
 2. The driving method of claim1, wherein (a) comprises: (a1) generating the noise signal correspondingto detected noise; and (a2) converting the noise signal into a digitalsignal.
 3. The driving method of claim 1, wherein said comparingincludes comparing the magnitude of the acquired noise signal with saidthreshold value that includes a plurality of different values.
 4. Thedriving method of claim 1, further comprising increasing a number ofsimultaneously driven driving electrodes of the capacitance-detectiondevice with an increase in the magnitude of the acquired noise signal.5. The driving method of claim 1, further comprising increasing asensing time of the capacitance-detection device with an increase in themagnitude of the acquired noise signal.
 6. The driving method of claim1, further comprising driving the capacitance-detection device at adriving speed that is not related to the magnitude of the acquired noisesignal.